1. Field of the Invention
This invention relates generally to postage meters and more particularly to providing a secure meter system wherein accounting data is stored in magnetic core memories.
2. Brief Description of the Prior Art
Security considerations have been significant in the design and construction of postage metering systems. Postal authorities have mandated security measures to insure that postage printed is accounted for. With many prior mechanical and electromechanical postage metering devices, security has been achieved through the employment of a housing which contains both the printing device and accounting registers. It should be appreciated that the accounting registers comprised gearing mechanisms arranged to incrementally drive register balance numeral wheels. A pair of registers were usually provided. One register, termed the incrementing register, stored the total value of postage dispensed by the meter. A second decrementing register was periodically recharged by postal authorities. During each postage printing transaction the amount of postage dispensed was subtracted from the decrementing register and added to the incrementing register. Thus, a double entry was maintained with regard to the amount of postage dispensed by the meter.
The employment of mechanical accounting registers provided a permanent record of the specific account of each meter with the integrity of such account being preserved against intentional and accidental destruction of the meter itself in the event of fire, explosion and the like. In the event of fire damage, it was usually possible to determine the settings on the register numeral wheels even if the temperatures reached during a fire were such that the numeral wheels no longer bore numeric indicia. In such instances, careful examination of the position of the gears in the registers resulted in a reconstruction of the specific register balance.
In U.S. Pat. No. 4,097,923 issued June 27, 1978 to Alton B. Eckert, Jr., Howell A. Jones, Jr. and Frank T. Check, Jr., and assigned to the assignee of the present invention, a typical microcomputerized electronic postage meter system was disclosed. Such systems greatly enhanced postage accounting capabilities and facilitated new meter designs, as well as fully automated mail handling systems wherein articles to be mailed were sealed, weighed, and the postage automatically applied thereto.
Security factors in processor controlled postage meter accounting necessitated certain design considerations. In the copending application of Robert B. McFiggans entitled System for Securing Postage Printing Transactions, Ser. No. 24,813 filed Mar. 28, 1979 and assigned to the assignee of the present invention, a postage meter having separable accounting and printing stations was disclosed. Thus, a removable accounting processor could be carried to the postal authorities for resetting without disturbing the postage printing station or other components of, for example, a large automated mailing console.
While the pending patent application of McFiggans above noted assured that postage would not be dispensed or printed without an accounting being maintained, security problems remained with regard to possible loss of accounting data stored in processor memories in the event the accounting processor memory was in an environment of highly elevated temperatures such as generated in a fire. Typical magnetic core memories comprising ferrite toroids which stored information at relatively high speeds with relatively low writing current suffered degradation with elevated temperatures and did thus not provide adequate thermal security for postage meter account balance purposes.
Semiconductor IC memories and MOS memories required battery backup for non-volatility and were subject to information loss through battery failure and otherwise at elevated temperatures.